Revert "net: add exit_batch_rtnl() method"

This reverts commit 041325b7 which is
commit fd4f101e upstream.

It breaks the Android kernel abi and can be brought back in the future
in an abi-safe way if it is really needed.

Bug: 161946584
Change-Id: Id0012b92edfa9cd162c757e0b35b1bb70473c140
Signed-off-by: Greg Kroah-Hartman <gregkh@google.com>